JP6901919B2 - Ship - Google Patents

Description

The present invention relates to a ship including a propulsion engine fueled by LPG.

In conventional ships, the fuel for the propulsion engine is generally fuel oil such as heavy oil or LNG (Liquefied Natural Gas). In recent years, it has also been proposed to use LPG (Liquefied Petroleum Gas) as a fuel for a propulsion engine.

For example, Patent Document 1 discloses a ship that supplies LPG as a liquid from a fuel tank to a propulsion engine. When LPG is used as fuel, it has the advantages of not requiring measures against sulfur oxides and less carbon dioxide emissions than fuel oil, and because it has a larger specific gravity than LNG, the fuel tank can be miniaturized. There is a merit.

Korean Publication No. 2012-0113398 Gazette

When LPG is used as fuel, the fuel tank and the propulsion engine can be connected by a fuel supply line and a fuel recovery line, and the required amount of LPG can be used in the engine while circulating LPG between the fuel tank and the engine. Conceivable.

By the way, when a low boiling point fuel such as LNG or LPG is used as the fuel for the propulsion engine, it is common to purge the fuel pipe in the engine room with an inert gas when the fuel is not used and in an emergency. Is necessary for. However, in the configuration using the fuel supply line and the fuel recovery line as described above, it is difficult to expel the liquid LPG out of the engine room by supplying the inert gas.

Therefore, an object of the present invention is to provide a ship capable of easily purging a portion existing in an engine room in a fuel supply line and a fuel recovery line through which LPG flows with an inert gas.

In order to solve the above problems, the vessel of the present invention supplies a fuel tank for storing LPG, a propulsion engine using LPG as fuel, a propulsion engine arranged in an engine room, and LPG from the fuel tank to the engine. A fuel supply line provided with a first shutoff valve outside the engine room and a fuel recovery provided with a second shutoff valve outside the engine room for recovering unused LPG from the engine to the fuel tank. The engine room is provided by a line, a first purge line for supplying an inert gas to the fuel recovery line between the engine room and the second shutoff valve, and a second purge line provided with a third shutoff valve. A purge tank connected to the fuel supply line with the first shutoff valve is provided, and the second purge line and the purge tank are a portion of the fuel supply line that exists in the engine chamber and the fuel. It is characterized in that it is arranged below the portion existing in the engine room in the recovery line.

According to the above configuration, the second purge line and the purge tank are arranged below the portion of the fuel supply line and the fuel recovery line that exists in the engine room. Therefore, when purging the portion of the fuel supply line and the fuel recovery line in the engine room with an inert gas, the first shutoff valve and the second shutoff valve are closed, the third shutoff valve is opened, and the first purge is performed. If an inert gas is supplied to the fuel recovery line through the line, LPG can be expelled from the fuel supply line into the purge tank using gravity. Therefore, the portion existing in the engine room in the fuel supply line and the fuel recovery line through which LPG flows can be easily purged with the inert gas.

The portion of the fuel supply line in the engine room may be uphill towards the engine and the portion of the fuel recovery line in the engine room may be downhill towards the engine. .. According to this configuration, the portion of the fuel supply line and the fuel recovery line existing in the engine room can be more easily purged with the inert gas.

The ship further comprises a heater that heats the LPG supplied to the fuel tank to 0 ° C. or higher, and the fuel tank holds the LPG at a pressure equal to or higher than the saturated vapor pressure at the temperature inside the fuel tank. You may. According to this configuration, the pipes constituting the fuel tank, the fuel supply line, and the fuel recovery line can be composed of a general steel material instead of a low-temperature steel material such as a nickel-based alloy, so that the cost can be reduced. ..

The fuel recovery line may be provided with a cooler that cools the LPG to a predetermined temperature. According to this configuration, it is possible to prevent the recovered LPG from flushing (rapidly vaporizing) in the fuel tank.

The fuel recovery line is provided with a pressure regulating valve, in which the pressure of the LPG on the upstream side of the pressure regulating valve is assumed to be the saturated steam pressure at the temperature of the LPG at the outlet of the engine or assumed. It may be adjusted to be higher than the saturated vapor pressure at the maximum temperature. According to this configuration, it is possible to prevent the LPG from flushing in the fuel recovery line.

The fuel tank may include a storage tank into which LPG is introduced and a service tank to which LPG is supplied from the storage tank and connected to the engine by the fuel supply line and the fuel recovery line. According to this configuration, the fuel tank can be divided into a storage tank for introducing LPG and a service tank for circulating LPG.

An inert gas may be introduced into the service tank. According to this configuration, the holding pressure of the service tank can be made higher than the saturated steam pressure, and it becomes easy to secure the required effective suction head (NPSHr) of the pump that supplies LPG to the engine.

The purge tank is connected to the fuel tank by a return line provided with a fourth shutoff valve, and the ship is the first shutoff valve, the second shutoff valve, the third shutoff valve, and the first shutoff valve. 4 A control device for controlling a shutoff valve is further provided, and the control device uses the third shutoff valve when the LPG is circulated between the fuel tank and the engine through the fuel supply line and the fuel recovery line. Upon closing, the first shutoff valve and the second shutoff valve are opened, and a purging operation of purging the portion of the fuel supply line in the engine chamber and the portion of the fuel recovery line in the engine chamber with an inert gas. The first shutoff valve, the second shutoff valve, and the fourth shutoff valve may be closed and the third shutoff valve may be opened, and the fourth shutoff valve may be opened after the purging operation is completed. .. According to this configuration, after the purging operation is completed, the pressure of the inert gas can be used to return the LPG accumulated in the purge tank to the fuel tank through the return line.

For example, the above-mentioned ship further includes a pressure gauge for detecting the pressure of the purge tank, and the control device performs the purge when the pressure of the purge tank detected by the pressure gauge becomes a predetermined value or more. It may be determined that the work has been completed.

According to the present invention, the portion existing in the engine room in the fuel supply line and the fuel recovery line through which LPG flows can be easily purged with the inert gas.

It is a schematic block diagram of the ship which concerns on one Embodiment of this invention.

FIG. 1 shows a ship 1 according to an embodiment of the present invention. The ship 1 includes a propulsion engine 12 that uses LPG as fuel and a fuel tank 2 that stores LPG. The main component of LPG may be propane (propane gas) or butane (butane gas).

The ship 1 is formed with an engine room 11, a relatively narrow first equipment room 14, and a relatively large second equipment room 15. The propulsion engine 12 is arranged in the engine room 11. Further, in the engine room 11, a boiler 13 for burning PG vaporized by LPG is also arranged. For example, the propulsion engine 12 is a diesel cycle or Otto cycle reciprocating engine. The second equipment room 15 does not necessarily have to be a closed space, and may be an open space (open space).

In the present embodiment, the fuel tank 2 has a storage tank 21 having a relatively large volume arranged outside all the rooms 11, 14 and 15 and a relatively small volume arranged inside the second equipment room 15. It is composed of the service tank 22 of the above. The storage tank 21 and the service tank 22 are connected to each other by a relay line 26.

LPG is introduced into the storage tank 21 from the LPG supply source through the fuel introduction line 23. The LPG supply source may be a cargo tank mounted on the ship 1, an LPG supply facility on land, or an LPG fuel supply ship.

In the present embodiment, the storage tank 21 is not provided with a device for adjusting the temperature, and the temperature of the storage tank 21 changes according to the atmospheric temperature. On the other hand, the LPG introduced from the LPG source is often about −42 ° C. Therefore, the fuel introduction line 23 is provided with a heater 24 for heating the LPG to 0 ° C. or higher. Then, the storage tank 21 holds the LPG at a pressure equal to or higher than the saturated steam pressure at the temperature inside the storage tank 21. However, if the land-based LPG supply facility or the LPG fuel supply ship, which is the LPG supply source, is equipped with a heater and the temperature of the LPG delivered to the ship 1 is 0 ° C. or higher, the heater 24 is unnecessary. ..

The holding pressure of the storage tank 21 means the pressure of the gas phase in the storage tank 21 (the same applies to the holding pressure of the service tank 22 described later). If no gas other than PG is mixed in the storage tank 21, the holding pressure of the storage tank 21 becomes equal to the saturated vapor pressure of LPG.

For example, when the temperature inside the storage tank 21 is 25 ° C., the holding pressure (saturated steam pressure) of the storage tank 21 is about 1.0 MPa in absolute pressure. Hereinafter, the pressure indication is an absolute pressure unless otherwise specified. Since the saturated vapor pressure of LPG is about 1.8 MPa at 50 ° C., the storage tank 21 is configured to withstand up to 1.9 MPa, for example.

A pump 25 is installed inside the storage tank 21. The number of pumps 25 may be one or plural. The upstream end of the relay line 26 described above is connected to the pump 25. Further, the downstream end of the relay line 26 is open in the service tank 22. Then, the pump 25 supplies LPG from the storage tank 21 to the service tank 22 through the relay line 26. However, the pump 25 may be provided outside the storage tank 21 in the middle of the relay line 26.

Like the storage tank 21, the service tank 22 is not provided with a device for adjusting the temperature, and the temperature of the service tank 22 changes according to the atmospheric temperature. The service tank 22 holds the LPG at a pressure equal to or higher than the saturated steam pressure at the temperature inside the service tank 22.

In the present embodiment, the service tank 22 is connected to the inert gas supply source (not shown) by the inert gas introduction line 54. The inert gas supply source is arranged, for example, in the engine room 11. When an inert gas (for example, nitrogen) is introduced into the service tank 22 through the inert gas introduction line 54, the holding pressure of the service tank 22 becomes higher than the saturated steam pressure. However, when there is no inert gas in the service tank 22, the holding pressure of the service tank 22 becomes equal to the saturated steam pressure of LPG.

When the LPG is circulated between the engine 12 and the service tank 22 as described later, the temperature of the service tank 22 may be higher than the atmospheric temperature. For example, when the temperature inside the service tank 22 is 40 ° C., the holding pressure (saturated steam pressure) of the service tank 22 is about 1.45 MPa. The service tank 22 is configured to withstand up to 2.0 MPa, for example.

The inert gas introduction line 54 is provided with a shutoff valve 55 and a pressure regulating valve 56 in this order from the upstream side. For example, the pressure of the above-mentioned inert gas supply source is 3.0 MPa. The shutoff valve 55 and the pressure regulating valve 56 are controlled by the control device 8. However, in FIG. 1, only some signal lines are drawn for the sake of simplification of the drawing. The control device 8 is, for example, a computer having a memory such as a ROM or a RAM and a CPU, and a program stored in the ROM is executed by the CPU.

The control device 8 is electrically connected to a pressure gauge 91 that detects the pressure (holding pressure) of the gas phase in the service tank 22. Then, the control device 8 controls the shutoff valve 55 and the pressure adjusting valve 56 so that the pressure detected by the pressure gauge 91 does not fall below the lower limit of the allowable range.

Further, the service tank 22 is connected to the boiler 13 described above by a combustion line 73. The upstream end of the combustion line 73 is connected to the upper part of the service tank 22. The combustion line 73 is provided with a pressure regulating valve 74 and a heater 75 in this order from the upstream side. The heater 75 heats the mixed gas of the vaporized PG and the inert gas to a temperature suitable for combustion in the boiler 13.

The pressure regulating valve 74 is controlled by the control device 8. The control device 8 controls the pressure regulating valve 74 so that the pressure detected by the pressure gauge 91 does not exceed the upper limit of the allowable range. Although not shown, the combustion line 73 is also provided with a pressure adjusting valve for reducing the pressure of the mixed gas supplied to the boiler 13 to 1.0 MPa or less.

Further, the service tank 22 is connected to the propulsion engine 12 by a fuel supply line 31 and a fuel recovery line 41. That is, LPG is supplied from the service tank 22 to the engine 12 through the fuel supply line 31, and unused LPG is recovered from the engine 12 to the service tank 22 through the fuel recovery line 41. In other words, LPG circulates between the service tank 22 and the engine 12 through the fuel supply line 31 and the fuel recovery line 41.

The upstream end of the fuel supply line 31 is connected to the lower part of the service tank 22. On the other hand, the portion 31a of the fuel supply line 31 existing in the engine room 11 (hereinafter, referred to as an extension portion in the engine room) has an upward slope toward the engine 12.

The fuel supply line 31 is provided with a pump 32, a heater 33, and a shutoff valve 34 (corresponding to the first shutoff valve of the present invention) in this order from the upstream side. These devices 32 to 34 are arranged outside the engine room 11. More specifically, the pump 32 and the heater 33 are arranged in the second equipment room 15, and the shutoff valve 34 is arranged in the first equipment room 14. The heater 33 heats the LPG to the required temperature of the engine 12 (for example, 45 ° C.).

The shutoff valve 34 is controlled by the control device 8. The control of the shutoff valve 34 will be described in detail later.

The downstream end of the fuel recovery line 41 is open in the service tank 22. On the other hand, the portion 41a of the fuel recovery line 41 existing in the engine room 11 (hereinafter, referred to as an extension portion in the engine room) has a downward slope toward the engine 12.

The fuel recovery line 41 includes a first pressure regulating valve 42, a shutoff valve 43 (corresponding to the second shutoff valve of the present invention), a cooler 44, and a second pressure regulating valve 45 (pressure adjusting of the present invention) in this order from the upstream side. (Equivalent to a valve) is provided. These devices 42 to 45 are arranged outside the engine room 11. More specifically, the first pressure regulating valve 42 and the shutoff valve 43 are arranged in the first equipment room 14, and the cooler 44 and the second pressure adjusting valve 45 are arranged in the second equipment room 15. The cooler 44 cools the LPG to a predetermined temperature (eg, 40 ° C.).

The first pressure regulating valve 42, the shutoff valve 43, and the second pressure regulating valve 45 are controlled by the control device 8. The control of the shutoff valve 43 will be described in detail later. The control device 8 is electrically connected to a pressure gauge 92 that detects the pressure of LPG at the inlet of the engine 12 and a pressure gauge 93 that detects the pressure of LPG on the upstream side of the second pressure regulating valve 45. In the present embodiment, the pressure gauge 93 is located on the downstream side of the cooler 44, but the pressure gauge 93 may be located on the upstream side of the cooler 44.

Regarding the first pressure regulating valve 42, the control device 8 controls the first pressure regulating valve 42 so that the pressure detected by the pressure gauge 92 becomes the required pressure of the engine 12. On the other hand, with respect to the second pressure regulating valve 45, the temperature of the LPG becomes slightly higher as the LPG passes through the engine 12 (for example, 55 ° C.). Therefore, as a set value for controlling the second pressure regulating valve 45, a set value such that the saturated steam pressure at the assumed maximum temperature is determined (for example, 2.0 MPa), and the control device 8 uses the pressure gauge 93. The second pressure regulating valve 45 is controlled so that the pressure detected in is higher than the set value.

Alternatively, the control device 8 is electrically connected to a thermometer 81 that detects the temperature of LPG at the outlet of the engine 12, and the pressure detected by the pressure gauge 93 is the temperature detected by the thermometer 81. The second pressure regulating valve 45 may be controlled so as to be higher than the saturated steam pressure of.

In the present embodiment, the portion between the heater 33 and the first shutoff valve 34 in the fuel supply line 31 is connected to the portion between the shutoff valve 43 and the cooler 44 in the fuel recovery line 41 by the bypass line 16. ing. The bypass line 16 is provided with a flow control valve 17. The flow rate control valve 17 is controlled by the control device 8 so that the LPG passing through the engine 12 has a predetermined flow rate.

Further, in the ship 1, the first purge line 51, as a configuration for purging the extension portion 31a in the engine room of the fuel supply line 31 and the extension portion 41a in the engine room of the fuel recovery line 41 with an inert gas, A second purge line 61 and a purge tank 6 are provided.

The first purge line 51 connects the portion of the fuel recovery line 41 between the engine room 11 and the first pressure regulating valve 42 to the above-described inert gas supply source (not shown). That is, the inert gas is supplied to the fuel recovery line 41 between the engine room 11 and the first pressure regulating valve 42 through the first purge line 51. The first purge line 51 is provided with a shutoff valve 52 and a flow rate control device in this order from the upstream side. The flow rate control device is the flow rate control valve 53 in this embodiment, but may be an orifice or the like.

The second purge line 61 connects the portion of the fuel supply line 31 between the shutoff valve 34 and the engine room 11 to the purge tank 6. The downstream end of the second purge line 61 is open in the purge tank 6. The second purge line 61 is provided with a shutoff valve 62 (corresponding to the third shutoff valve of the present invention).

The second purge line 61 and the purge tank 6 are arranged in the first equipment room 14 below the extension portion 31a in the engine room of the fuel supply line 31 and the extension portion 41a in the engine room of the fuel recovery line 41. ing.

Further, the purge tank 6 is connected to the service tank 22 by the return line 63 and is connected to the boiler 13 described above by the combustion line 71. The return line 63 is for returning the liquid LPG to the service tank 22, and the combustion line 71 is for guiding the mixed gas of the vaporized PG and the inert gas to the boiler 13.

The upstream end of the return line 63 is open in the purge tank 6, and the downstream end of the return line 63 is open in the service tank 22. The return line 63 is provided with a shutoff valve 64 (corresponding to the fourth shutoff valve of the present invention).

The upstream end of the combustion line 71 is connected to the upper part of the purge tank 6. The combustion line 71 is provided with a shutoff valve 72. Although not shown, the combustion line 71 is also provided with a pressure adjusting valve for reducing the pressure of the mixed gas supplied to the boiler 13 to 1.0 MPa or less.

The shutoff valves 52, 62, 64, 72 and the flow rate control valve 53 described above are controlled by the control device 8. Hereinafter, the control of these valves will be described including the control of the shutoff valve 34 of the fuel supply line 31 and the shutoff valve 43 of the fuel recovery line 41.

When the LPG is circulated between the service tank 22 and the engine 12 through the fuel supply line 31 and the fuel recovery line 41, the control device 8 shuts off the shutoff valve 52 of the first purge line 51 and the shutoff of the second purge line 61. The valve 62, the shutoff valve 64 of the return line 63, and the shutoff valve 72 of the combustion line 71 are closed, and the shutoff valve 34 of the fuel supply line 31 and the shutoff valve 43 of the fuel recovery line 41 are opened. As a result, LPG circulates through the fuel supply line 31 and the fuel recovery line 41.

On the other hand, when performing a purging operation of purging the extension portion 31a in the engine room of the fuel supply line 31 and the extension portion 41a in the engine room of the fuel recovery line 41 with an inert gas, the control device 8 uses the fuel supply line 31. The first shutoff valve 34 and the shutoff valve 43 of the fuel recovery line 41 are closed, and the shutoff valve 52 of the first purge line 51 and the shutoff valve 62 of the second purge line 61 are opened. At this time, the shutoff valve 64 of the return line 63 and the shutoff valve 72 of the combustion line 71 remain closed.

As a result, while the inert gas is supplied to the fuel recovery line 41, the upstream side including the engine room extending portion 41a of the fuel recovery line 41 and the downstream side including the engine room extending portion 31a of the fuel supply line 31. The LPG present in the portion is expelled into the purge tank 6. Along with this, the pressure in the purge tank 6 gradually increases. At this time, the control device 8 controls the flow rate control valve 53 to adjust the flow rate of the inert gas.

The pressure of the purge tank 6 depends on the amount of inert gas passing through the extending portion 41a in the engine room of the fuel recovery line 41 and the extending portion 31a in the engine room of the fuel supply line 31.

Therefore, when the pressure detected by the pressure gauge 94 becomes a predetermined value (purge completion pressure: for example, 1.9 MPa) or more corresponding to the amount of the inert gas to be flowed, the control device 8 performs the purging operation. Judge as completed. Further, when the pressure required for returning LPG from the purge tank 6 to the service tank 22 (necessary pressure for returning LPG: for example, 2.0 MPa in gauge pressure) is higher than the purge completion pressure, the control device 8 further increases the pressure. The shutoff valve 52 of the first purge line 51 and the shutoff valve 62 of the second purge line 61 are kept open so that the purge tank 6 is continuously pressurized. Then, when the pressure of the purge tank 6 becomes equal to or higher than the pressure required for returning the LPG, the control device 8 closes the shutoff valve 52 of the first purge line 51 and the shutoff valve 62 of the second purge line 61, and then the return line. The shutoff valve 64 of 63 is opened. As a result, after the completion of the purging operation, the LPG accumulated in the purge tank 6 can be returned to the service tank 22 through the return line 63 by utilizing the pressure of the inert gas.

When the return of the LPG to the service tank 22 is completed, the control device 8 closes the shutoff valve 64 of the return line 63 and opens the shutoff valve 72 of the combustion line 71, and the PG and the inert gas remaining in the purge tank 6 are opened. Is supplied to the boiler 13.

As described above, in the ship 1 of the present embodiment, the second purge line 61 and the purge tank 6 are from the engine room extending portion 31a of the fuel supply line 31 and the engine room extending portion 41a of the fuel recovery line 41. Is also located below. Therefore, when purging the extension portion 41a in the engine room of the fuel recovery line 41 and the extension portion 31a in the engine room of the fuel supply line 31 with an inert gas, LPG is supplied from the fuel supply line 31 by using gravity. It can be expelled into the purge tank 6. Therefore, the extending portion 41a in the engine room of the fuel recovery line 41 and the extending portion 31a in the engine room of the fuel supply line 31 can be easily purged with the inert gas.

Further, in the present embodiment, since the LPG introduced into the storage tank 21 is heated to 0 ° C. or higher by the heater 24, the storage tank 21 and the service tank 22, the fuel supply line 31, and the fuel recovery line 41 are configured. The pipe can be made of a general steel material instead of a low temperature steel material such as a nickel-based alloy. Therefore, the cost can be reduced.

Further, in the present embodiment, since the cooler 44 is provided in the fuel recovery line 41, it is possible to prevent the recovered LPG from flushing (rapidly vaporizing) in the service tank 22.

Further, in the present embodiment, the pressure of the LPG on the upstream side of the second pressure regulating valve 45 is adjusted by the second pressure regulating valve 45 of the fuel recovery line 41 so as to be higher than the saturated steam pressure at the assumed maximum temperature. Therefore, it is possible to prevent the LPG from flushing in the fuel recovery line 41 (in this embodiment, before the LPG is cooled by the cooler 44).

(Modification example)
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

For example, if the return line 63 is provided with a check valve, the shutoff valve 64 does not have to be closed when the LPG is circulated between the service tank 22 and the engine 12.

Further, in the above embodiment, the fuel tank 2 is composed of the storage tank 21 and the service tank 22, but the storage tank 21 may be omitted and the fuel tank 2 may be composed of only the service tank 22. However, with the configuration as in the above embodiment, the fuel tank 2 can be divided into a storage tank 21 for introducing LPG and a service tank 22 for circulating LPG.

Further, the extending portion 31a in the engine room of the fuel supply line 31 does not necessarily have to have an upward slope toward the engine 12, and may be arranged on a horizontal plane. Similarly, the extending portion 41a in the engine room of the fuel recovery line 41 does not necessarily have to have a downward slope toward the engine 12, and may be arranged on a horizontal plane. However, with the configuration as in the above embodiment, the extension portion 41a in the engine room of the fuel recovery line 41 and the extension portion 31a in the engine room of the fuel supply line 31 can be more easily purged with the inert gas. it can.

Further, the inert gas does not necessarily have to be introduced into the service tank 22, and the holding pressure of the service tank 22 may be equal to the saturated steam pressure of LPG. However, with the configuration as in the above embodiment, the holding pressure of the service tank 22 can be made higher than the saturated steam pressure, and the required effective suction head (NPSHr) of the pump 32 that supplies LPG to the engine 12 is secured. Will be easier.

Further, the shutoff valve 72 of the combustion line 71 may be omitted, and the pressure adjusting valve (not shown) of the combustion line 71 may be fully closed until the return of LPG from the purge tank 6 to the service tank 22 is completed.

Further, the return line 63 may be omitted, and after the purging operation is completed, the entire amount of LPG accumulated in the purge tank 6 may be vaporized and supplied to the boiler 13 through the combustion line 71.

1 Ship 11 Engine room 12 Propulsion engine 2 Fuel tank 21 Storage tank 22 Service tank 24 Heater 25 Pump 31 Fuel supply line 31a Extension in engine room 34 Shutoff valve (1st shutoff valve)
41 Fuel recovery line 41a Extension in the engine room 43 Shutoff valve (second shutoff valve)
51 1st purge line 6 Purge tank 61 2nd purge line 62 Shutoff valve (3rd shutoff valve)
63 Return line 64 Shutoff valve (4th shutoff valve)
8 Control device

Claims (9)

A fuel tank that stores LPG and
A propulsion engine placed in the engine room that uses LPG as fuel,
A fuel supply line provided with a first shutoff valve outside the engine room, which supplies LPG from the fuel tank to the engine, and
A fuel recovery line provided with a second shutoff valve outside the engine room for recovering unused LPG from the engine to the fuel tank.
A first purge line that supplies an inert gas to the fuel recovery line between the engine room and the second shutoff valve.
A second purge line provided with a third shutoff valve comprises a purge tank connected to the fuel supply line between the engine room and the first shutoff valve.
A ship in which the second purge line and the purge tank are arranged below a portion of the fuel supply line in the engine room and a portion of the fuel recovery line in the engine room. The portion of the fuel supply line that resides in the engine room is an uphill slope towards the engine.
The ship according to claim 1, wherein the portion of the fuel recovery line existing in the engine room has a downward slope toward the engine. A heater for heating the LPG supplied to the fuel tank to 0 ° C. or higher is further provided.
The ship according to claim 1 or 2, wherein the fuel tank holds LPG at a pressure equal to or higher than the saturated vapor pressure at the temperature inside the fuel tank. The ship according to any one of claims 1 to 3, wherein the fuel recovery line is provided with a cooler for cooling LPG to a predetermined temperature. The fuel recovery line is provided with a pressure regulating valve, in which the pressure of the LPG on the upstream side of the pressure regulating valve is assumed to be the saturated steam pressure at the temperature of the LPG at the outlet of the engine or assumed. The vessel according to any one of claims 1 to 4, which is adjusted to be higher than the saturated steam pressure at the maximum temperature. The fuel tank includes a storage tank into which LPG is introduced, and a service tank to which LPG is supplied from the storage tank, which is connected to the engine by the fuel supply line and the fuel recovery line. The ship described in any one of the above. The ship according to claim 6, wherein an inert gas is introduced into the service tank. The purge tank is connected to the fuel tank by a return line provided with a fourth shutoff valve.
A control device for controlling the first shutoff valve, the second shutoff valve, the third shutoff valve, and the fourth shutoff valve is further provided.
When the control device circulates LPG between the fuel tank and the engine through the fuel supply line and the fuel recovery line, the control device closes the third shutoff valve and closes the first shutoff valve and the second shutoff. When the valve is opened and the purging operation of purging the portion existing in the engine room in the fuel supply line and the portion existing in the engine room in the fuel recovery line with an inert gas is performed, the first shutoff valve, said The vessel according to any one of claims 1 to 7, wherein the second shutoff valve and the fourth shutoff valve are closed, the third shutoff valve is opened, and the fourth shutoff valve is opened after the purging operation is completed. .. Further equipped with a pressure gauge for detecting the pressure of the purge tank,
The ship according to claim 8 , wherein the control device determines that the purging operation is completed when the pressure of the purge tank detected by the pressure gauge becomes a predetermined value or more.

Images